The retiring NIH director, whose last day was Sunday, cautioned on NPR´s Weekend Edition that the highly transmissible Omicron variant could still spark millions of cases in the U.S., even if it ends up causing milder disease.

“Even if it has a somewhat lower risk of severity, we could be having a million cases a day if we’re not really attentive to all of those mitigation strategies,” he said. “And you know a small fraction of a big number is still a really big number.”

While at least 43 states have detected the omicron strain, scientists say the current increases in cases, hospitalizations and deaths can be attributed to the delta variant, which the Centers for Disease Control and Prevention (CDC) estimates makes up nearly 97% of all US Covid-19 cases.

Increased spread of the omicron variant with 57 different mutations could further strain US testing capacity and hospitals, experts have said.

Collins said he worries a lot about the stressed health care system and the possibility of temporarily losing health care workers who catch the virus.

¨I know people are tired of this,¨ he said. ¨I´m tired of it too, believe me. But the virus is not tired of us.¨

The CDC considers a majority of counties in the U.S. to have high and substantial transmission ahead of the holiday weekend.

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